Hannu Krosing wrote:
> Ühel kenal päeval, L, 2007-02-17 kell 22:49, kirjutas Chad Wagner:
>>         However, they don't have vacuum, we do.
>> Right, and I think that is more or less because Oracle doesn't need
>> it.  Vacuum's main purpose (correct me if I am wrong) is to
>> recover/mark rows that are no longer used, and Oracle essentially
>> reuses the space immediately. 
>> Obviously with Oracle if you bloat out a table and delete a ton of
>> rows then you have to rebuild the table, but that is more or less the
>> same problem that PostgreSQL has and where vacuum full comes into
>> play.
>> The only benefit with the Oracle model is that you can achieve
>> flashback, which is a very rarely used feature in my book.
> We can have flashbacks up to the last vacuum. It is just not exposed.
> Don't vacuum, and you have the whole history. (Actually you can't go for
> more than 2G transactions, or you get trx id rollover).
> To get a flashback query, you "just" have to construct a snapshot from
> that time and you are done. We don't store transaction times anywere, so
> the flashback has to be by transaction id, but there is very little
> extra work involved. We just don't have syntax for saying "SELECT ... AS

Well this is certainly interesting. What do we think it would take to
enable the functionality?

Joshua D. Drake


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